March 10 (Bloomberg) -- The cooling in the Pacific Ocean
known as La Nina, which can influence Atlantic hurricanes and
U.S. drought, is expected to keep fading and vanish by June,
according to U.S. forecasters.

Observations and computer models agree on the weakening of
the phenomenon, which also has been blamed for flooding in
Australia, the U.S. Climate Prediction Center said today in a
report on its website. Forecasters can’t predict whether it will
remain weak or pick up strength after July, the agency said.

Neutral temperatures in the Pacific won’t do anything to
diminish the number of Atlantic hurricanes this year, said
William Gray, who makes seasonal hurricane forecasts at Colorado
State University in Fort Collins.

“We’re forecasting a pretty active season for this year
and we probably won’t change that much,” Gray said. “We can
have very active seasons when it is neutral.”

The phenomenon peaked in early January and has diminished
since, according to the Australian Bureau of Meteorology, which
also tracks La Nina.

“La Nina will continue to have global impacts even as the
episode weakens through the Northern Hemisphere spring,” the
U.S. center said. In the U.S., the effects from March through
May may include below-normal rain across the South and Plains,
and higher temperatures for the southern half of the country.

On average, La Nina occurs every three to five years and
lasts nine to 12 months, with some persisting as long as two
years.

The phenomenon has been blamed for enhancing hurricane
development in the Atlantic by limiting wind shear there that
can tear budding storms apart.

In December, Colorado State predicted 17 named storms, with
winds of at least 39 miles per hour, would form in the Atlantic
this year, nine of them becoming hurricanes with at least 74 mph
winds. The university will update its forecast in April.

Hurricane Season

Last year, while La Nina gained strength, 19 named storms
formed in the Atlantic, tying it for the third-most-active
season on record with 1995 and 1887, according to the U.S.
National Hurricane Center. A record 28 storms formed in 2005.

Hurricane season starts on June 1 and ends on Nov. 30.

Some forecast models predict the Pacific will return to
neutral conditions, between a La Nina and the above-average
warming known as El Nino.

Gray said getting an accurate read on what La Nina will do
in three months’ time is difficult because forecasting
confidence falls during March, April and May. Those three months
are often called the “spring barrier” by U.S. forecasters.

“It is a tough barrier, you don’t know what is going to
happen,” Gray said.

Meteorologist Allen Motew said he thinks La Nina won’t fade
at all. While it may weaken, the Pacific will likely stay cool
through next year, said Motew, a forecaster at QT Weather in
Chicago.

“It may get near neutral around July but not quite make it
and then go into a stronger La Nina in late summer and fall,”
Motew said.

That would mean agricultural areas across the southern U.S.
may face drought, he said.

The next Australian update on La Nina will be March 16,
while the U.S. will revise its forecast in April.